This invention relates generally to apparatus for the electrostatic transfer of a developed image from a master to a receiving surface. More specifically, it pertains to the carrier backing means and the cooperation with the movable transfer means that contacts and traverses the flexible carrier means which supports the master to effect the electrostatic transfer.
The permanent master and the transfer means are used repeatedly to produce high resolution and high quality images on receiving surfaces, such as printed circuit boards. Receiving surfaces, such as printed circuit boards, have traditionally been produced by individual laminating, exposing, developing, etching and stripping processes where dry film photoresist has been used to produce the conductive wiring patterns. Heretofore, there has been no method or apparatus available to produce a plurality of copies of conductive wiring patterns from a single master copy of the desired wiring pattern utilizing a dry film resist and photoimaging. There are many factors which prevented this type of a system from being employed to manufacture multiple copies from a single master.
Where liquid toner was employed, it was extremely difficult to attempt to clean excess toner or prevent the buildup of excess toner from the master. The ability to obtain a uniform and full width image over a large area, such as a 24 inch by 24 inch surface, was severely restricted. Trapped air or excess liquid solvent can frequently cause voids in the electrostatically transferred developed image. The ability to clean off residual toner from the master prior to transferring each additional electrostatically developed image is important. Where electrostatics were used to effect the transfer, the ability to separate the master surface and the receiving surface was critical and extremely difficult because of the electrostatic forces involved. Lastly, the availability of reliable and durable equipment to effect repeated transfers of the developed image on a master to a receiving surface was severely limited.
These problems are solved in the design of the apparatus of the present invention by providing carrier backing means that cooperates with the transfer means which contacts the flexible carrier of the master to provide a flat surface and to maintain a uniform distance between the master and the component parts during development of the electrostatic image and cleaning of the master. The electrostatic transfer of a developed image to a receiving substrate is effected by traversing the carrier means for a distance equal to at least the length of the master.